Recovery of sulphur



July 27, 1937. v R. F. BACON ET Al. 2,087,894

. l RECOVERY oF sULPHUR Filed oct. 18, 1954 ATTORNEY5 Patented July 27, 1937 UNITED lSTATES tais-ai lianoovlsrw 0F SULPHUR Raymond F.

Bacon, Bronxville, N. Y., and Wilber Judson, Newgulf, Tex.

Applicaticn'October 18, 1934, Serial No. 748,953

l2 Claims.

This invention relates to the recovery of sulphur and has for an object the provision oi an improved process and apparatus for recovering elemental sulphur from metal sulphide-bearing material. 'templates the provision of an improved process and apparatus for recovering elemental sulphur from pyrites,

The present invention contemplates the effective utilization of heat capable of being developed by reactions involved in or associated with the oxidation of pyrites for the recovery of the volatile sulphur of the pyrites in elemental form. The method of the invention involves the oxidationof an iron sulphide product resulting from the distillation of pyrites under such conditions as to produce sufficient heat to eect the distillation of the pyrites. Y

According to the preferred method of the in- Vention, the iron sulphide residue from a pyrites distillation operation is subjected while molten to an oxidizing operation to produce iron oxide and a gaseous product containing sulphur dioxide. 'I'he oxidizing operation is so controlled that a substantially oxygen-free gaseous product containing suicient heat to eiectively distill the volatile sulphur of the quantity oi' the pyrites required to produce iron sulphide -for the oxidizing operation is formed. Distillation of the volatile sulphur of the pyrites'isveaccomplished by suspending the pyrites, in finely divided form, in the hot gaseous product of the oxidizing operation. The residue resulting from distillation of the pyrites, consisting substantially of the monosulphide of iron, is treated in the oxidizing operation. operation, containing the volatile sulphur of the pyrites in elemental yform and the sulphur dioxide produced in the oxidizing operation may be treated for the recovery of the sulphur of the sulphur dioxide either before or after cooling to condense the elemental sulphur.

The invention will be better understood from a consideration of the following description in conjunction'with the accompanying drawing showing schematically apparatus.V which maybe employed in carrying out a. process of the invention.

The apparatus shown in the drawing comprises oxidizing chambers I!) and I I in the form of molten bath receptacles, a distillation chamber IZ, heat exchangers I3 and I4, a dust collector I5, a condenser i3 and an electrical precipitator 9, all so connected by suitable means that iron sulphide-bearingr material maybe delivered from More particularly, the invention con- The gaseous product of the distillationV the distillation chamber to the oxidizing chambers and gases Vfrom the oxidizing chambers may be utilized in the distillation operation and then be subjected progressively to dust removing, cooling or condensing and precipitating treatments.

The oxidizing chambers Ill and II are similar in structure to ordinary copper converters, each 'comprising a steel outer shell lined with refractory material such as magnesite brick. The upper portions of the oxidizing chambers communicate thro-ugh branch conduits Il and I8 and a main conduit I9 with a screw conveyor 2li which is adapted to deliver materials to be treated from the lower portion of the distillation chamber to the oxidizing chambers. The branch conduits Il and I8 are provided with dampers or valves 2| and 22 whichmaybe manipulated to close off one or both of the oxidizingV chambersfrom communication with the screw conveyor 2li. The screw conveyor is so constructed and arranged that materials may. be delivered from the distillation chamber to the oxidizing chambers without admitting air to any chamber.` The lower portions of the oxidizing chambers are provided with tapping spouts 23 and 24 through which the molten oxidized product may be withdrawn upon completion of the oxidizing treatment.

The upper portions of the oxidizing chambers are tightly connected to conduits or flues 25 and 26 which are, in turn, tightly connected to the heat exchangers `I3 and I4. Annular. manifolds 21 and 28 surrounding the oxidizing chambers and communicating therewith through tuyres 3!! and 3l are provided for introducing air into the oxidizing chambers. f

The oxidizing chambers may be .stationary or mounted for tilting movement on any suitable ,type of supporting-structure. v v- The heat exchangers I3 and I4 comprise inner chambers 34 and 33 formed o-f good heatconducting material and'heat insulated jackets 32 and 35 surrounding the inner chambers and havl ing their walls spaced from the walls of the inner chambers to provide passages therebetween. The passages between the inner` chambers 32 and 33 andthe jackets 34 and 35 ofY the heat exchangers are provided withstaggeredbafes 36 and 3l for providing tortuous paths of travel for gases. Air may be admitted tothe passages between the inner chambers and the jackets through inlets 38 and 40, and heated air may be withdrawn through conduits 4I and 42 which communicate with the manifolds 2'! and 28 associated with the oxidizing chambers. Air inlets 43 and 44, open to the atmosphere or connected to suitable sources of air under pressure (not shown), communicate with the conduits il and 42. Blowers l5 and 45 are included in the conduits 4I and 42 to cause air to flow through the heat exchangers and to aid in introducing air and other oxidizing gases into the oxodizing chambers.

Conduits 4l and 48 having valves 39 and i9 included therein provide passages for conducting hot gases from the inner chambers 32 and 33 of the heat exchangers. to the distillation chamber i2. The conduit ll leading from the oxidizing chamber Il) and heat exchanger i3 is connected to the conduit 42 (through which oxidizing gases are introduced into the oxidizing chamber i i) ahead of the blower 45 by means of a conduit 2 having a valve 3 included therein. Similarly, the conduit 48 leading from the oxidizing chamber II and heat exchanger i4 is connected to the conduit 4I (through which oxidizing gases are introduced into the oxidizing chamber i8) ahead of the blower l5 by means of a conduit i having a valve included therein. rhe valves 3, 5, 39. and 49 may be manipulated to pass the gaseous product from chamber Iii through a molten bath in chamber i I or the gaseous product from chamber II thro-ugh a molten bath in chamber tu.

The distillation chamber is an upright cylindrical chamber lined with heat refractory mat/erial and covered with heat insulating material. The upper portion of the distillation chamber communicates with a screw conveyor 5i! which is adapted to deliver pyrites for treatment from a storage hopper 5i to the distillation chamber. The screw conveyor 56 is so constructed and arranged that materials may be delivered to the distillation chamber without admitting air. The distillation chamber is provided with a grate 52 for collecting agglomerations too large for convenient passage through the conveyor Zil. A work hole 53 provided with a suitable removable cover permits access to the interior of the chamber for the purpose of breaking or removing agglomerations collected on the grate 52. An annular manifold 54 surrounding the distillation chamber and communicating therewith through tuyres 55 is provided for introducing hot gases from the conduits 4l' and 48 leading from the heat exchangers into. the interior of the distillation chamber.

A conduit 56 provides a passage for conducting gases from the upper portion of the distillation chamber to the interior of the dust collector I5. The dust collector is provided with a series of baiiies 51 so arranged as to provide a tortuous path for the flow of gases between the inlet conduit 56 and an outlet 58. Thebottom of the dust collector is provided with a number of hoppers 69 for the reception of dust particles removed from the gas stream. The hoppers (SilV are provided with valved outlets 6I through which dust particles collected in the hoppers may be withdrawn. The dust collector outlet 58 co-mmunicates with the lower portion of the condenser I E.

The condenser I5 is in the form of a re tube boiler provided with a valved inlet 52 for water and a valved outlet SS for steam. Condensate formed in the condenser may be withdrawn from the lower portion thereof through a valved outletV 64. Gases may be conducted from the 'condenser through an outlet conduit 65 having a fan 66 included therein to the electrical precipitator 9 which may be of any suitable construction.

In employing the apparatusillustrated in the drawing for carrying out a method of the inventhe gases to aV temperature at which distillation of the Volatile sulphur of the pyrites is effected. The gaseous product containing the sulphur dioxide produced in the oxidizing chambers and the volatile sulphur` of the pyrites in the form of elemental sulphur vapor and a solid product comprising the residue of the pyrites, substantially in the form of monosulphide of iron, are thus produced. The gaseous product passes to the dust collector l5 through the outlet conduit 55. The solid residue from the pyrites is delivered to the screw conveyor 2Q which conveys it to the oxidizing chambers I@ and l I.

The iron sulphide-bearing material passes from the conveyor 25 through the main conduit l t and the branch conduits il and i8 into molten baths in the bottoms of the oxidizing chambers.

Operation of the oxidizing chambers may be initiated by melting a small charge of iron sulphide-bearing materials in the chambers by combustion of anyl suitable fuel or by retaining portions of molten baths produced in preceding operations.

Air is introduced into the molten baths within the oxidizing chambers through the tuyres 3B and 3i. The oxygenk of the air reacts with the iron sulphide to produce gaseous sulphur dioxide and molten iron oxide. The oxidation reaction is carried out at a temperature substantially above i000 C., and advantageously at about 12000 C. The introduction of iron sulphide-bearing material into the oxidizing chambers may be continued for periods varying from one to several hours until the operating capacity of each chamber has been reached. When charging has been completed, blowing is continued until substantially all sulphur has been removed. The resulting molten baths, consisting largely of iron oxide are then removed through the tapping spouts. Preferably, the operations of the two oxidizing chambers are staggered in order to permit charging and tapping atV different times and thus permit continuous operation of the process and the production of a substantially uniform sulphur dioxide product.

`The sulphur dioxide, together with the inert gases introduced into the oxidizing chambers with the air, passes through the conduits 25 and 26 to the heat exchangers I3 and. I4. The gases entering the heat exchangers, after having been cooled to the desired temperature, preferably in the neighborhood of 1009" C., flow through the conduits ll and i8 to the manifold 5t from where they enter the distillation chamber through the tuyres 55.

The oxidizing operationsare preferably so controlled that substantially oxygen-free gaseous products containing sulphur dioxide are introduced into the distillation chamber. Preferably, the gaseous products'introduced into the distillation chamber contain not more than about one percent of free oxygen. l

When the sulphur content of a charge in an oxidizing chamber is nearly exhausted, the-oxygen content of the gaseous product tends to increase. Introduction of the resulting gaseous. product of relatively high oxygen content into the distillation chamber may be avoided by passing the gaseous product through a molten bath of higher sulphur content in another oxidizing chamber.

When the charges in the oxidizing chambers contain suicient sulphur to insure the production of substantially oxygen-free gaseous products, the operations are conducted with valves 39 and I9 open, valves 3 and 5 closed and the Valves associated with the air inlets 43 and 44 and the air passages of the heat exchangers suitably adjusted to provide satisfactory volumes of oxidizing gas at proper temperatures. When the sulphur content of one of the charges becomes reduced to the point at Which the oxygen content of the gaseous product increases to an undesirable amount, the gaseous product is passed yin series with the other oxidizing chamber. In the staggered operation of the oxidizing chambers, the oxidizing operations are commenced at different times, and a charge containing sumcient sulphur to insure the production of a substantially oxygen-free gaseous product will always be un-` dergoing treatment. Staggering of the operations is carried out tomaintain in one chamber a charge containing suiiicient sulphur to insure the production of a substantially oxygenefree gaseous product until the sulphur of the charge in the other chamber has been substantially completely eliminated and the treatment of a fresh charge has been commenced after removal of the substantially sulphur-free charge.

The gaseous product formed in chamber I may be passed through a molten charge in chamber il by opening the valve 3, closing the valve 39 and suitably adjusting the valves associated' with the air inlet 44 and the air passage in the heat exchanger I4 to cause a flow of gases from the conduit 2 through the conduit 42 and blower llt. Similarly, the gaseous product formed in chamber II may be passed through a molten bath in chamber I by opening the valve 5, closing the valve 49 and suitably adjusting the valves associated with the air inlet 43 and the air passage in the heat exchanger I3 to cause a flow of gases from the conduit 4 through the conduit il and blower 55.

The sulphur-laden gases from the upper portion of the distillation chamber are introduced into the dust collector I5 through the conduit 56 and flow through the dust collector to the outlet 58. During the course of the passage of the sulphur-laden gases through the dust collector, substantially all dust particles are removed. The cleaned gases passing out of the dust collector through the conduit 58 enter the condenser I6 in which a temperature sufficiently low to effect condensation of the sulphur vapor contained in the gases is maintained. A temperature of about 115 C. to 150 C. is preferably maintained in the condenser. Sulphur dioxide-bearing gases are conducted from the condenser through the conduit 65 to the electrical precipitator 9 in which entrained sulphur particles may be removed. Molten sulphur collected in the lower portion of the condenser is withdrawn through the outlet 64. Sulphur dioxide-bearing gases expelled from the electrical precipitator may be treated in any suitable manner for the recovery of the sulphur dioxide or for the recovery in elemental form of the sulphur of the sulphur dioxide.Y

It is to be understood that the vapparatus illus- V trated in the drawing is merely illustrative and is notintended to be restrictive of the invention in any respect.

We claim:

1. The method of producing elemental sulphur` Which comprises subjecting iron sulphide-bearing material in the form of a molten bath to an oxidizing operation in such manner that a gaseous product containing sulphur dioxidey and some free oxygen is produced, passing said gaseous product through a second molten bath of iron sulphide-bearing material in such manner that at least a part of the free oxygen is eliminated from the gaseous product, and passing the resulting gaseous product in contact with finely divided pyrites in a suspension distillation chamber in such manner as to eect suspension distillation from the volatile sulphur of the pyrites.

2. The method of producing elemental sulphur which comprises subjecting iron sulphide-bearing material in the form of a molten bath to an oxidizing operation in which an oxidizing gas is passed in lcontact with the iron sulphide-bearing materialin such manner that a gaseous product containing sulphur dioxide and initially less than about one per cent of free oxygen is produced, passing the resulting gaseous product, While the oxygen content thereof remains below approximately one per cent, in contact with nely divided pyrites in a suspension distillation chamber in such a manner as to effect suspension distillation of the volatile sulphur of the pyrites, and passing the gaseous product through a second molten bath of iron sulphide-bearing material prior to the distilling operation when the oxygen content of the gaseous product from the rst molten bath exceeds approximately one per cent.

RAYMOND F. BACON. WILBER JUDSON. 

